<div class="container showgrid">
    <div class="span-24">
        头部页眉
    </div>
    <div class="span-4">
        左边侧栏
    </div>

    <div class="span-16">
        <div class="span-8">
            居中行1-1
        </div>
        <div class="span-4">
            居中行1-2
        </div>
        <div class="span-4 last">
            居中行1-3
        </div>
        <div class="span-16 last">
            正文内容
        </div>
    </div>

    <div class="span-4 last">
        右边侧栏
    </div>
    <div class="span-24">
        页脚
    </div>
</div>
